Wafer rotation device and edge flaw inspection apparataus having the device

ABSTRACT

A wafer rotating device  1  is provided with at least three rollers  2  rotatably provided about axes arranged at parallel intervals and which rotate over the circumferential surface of a disk-shaped wafer  5 , a rotation drive mechanism  3  that rotates and drives at least one of the rollers  2 , an interval adjustment mechanism  4  capable of adjusting the dimensions of the intervals of the rollers  2 , a load control device  6  that controls the load applied from the rollers  2  to the wafer  5  in the radial direction of the wafer  5  when the wafer  5  is clamped between rollers  2 . As a result, a silicon wafer can be rotated without contacting the top and bottom surfaces of the silicon wafer.

TECHNICAL FIELD

The present invention relates to a wafer rotating device that rotates asilicon wafer, semiconductor wafer or other part formed into the shapeof a disk, and an edge flaw inspection device provided therewith.

BACKGROUND ART

In the prior art, an example of an edge flaw inspection device forsearching for edge flaws such as cracks, chips or polishing flaws innarrow, long edges such as the peripheral edges of silicon wafers isdescribed in Japanese Patent No. 2999712.

This device is provided with a rotating table that horizontally rotatesa silicon wafer by suctioning the bottom of the silicon wafer at alocation near its center. Light is irradiated onto the edge of thesilicon wafer being horizontally rotated by this rotating table and thelight reflected by the edge is detected and analyzed to detect the typeof edge defect or surface roughness and so forth.

However, since the rotating table of this device suctions the bottom ofa silicon wafer, inspections cannot be carried out after the top andbottom of the silicon wafer have been polished, thereby enablinginspections to only be carried out before the top and bottom of thesilicon wafer are polished.

Since edge defects have a high potential to expand or occur due tostress generated during polishing of the tops and bottoms of siliconwafers, it is preferable to inspect for edge defects and so forth afterpolishing the top and bottom of silicon wafers.

In consideration of these circumstances, an object of the presentinvention is to provide a wafer rotating device that enables siliconwafers to be rotated without contacting the top and bottom of thesilicon wafer, and an edge flaw inspection device provided with thiswafer rotating device.

DISCLOSURE OF THE INVENTION

A wafer rotating device of the present invention is provided with atleast three rollers rotatably provided about axes arranged at parallelintervals and which rotate over the circumferential surface of adisk-shaped wafer, a rotation drive mechanism that rotates and drives atleast one of the rollers, an interval adjustment mechanism capable ofadjusting the dimensions of the intervals of the rollers, and a loadcontrol device that controls the load applied from the rollers to thewafer in the radial direction of the wafer when the wafer is clampedbetween the rollers.

According to this device, by operating the internal adjustment mechanismwith a disk-shaped wafer arranged between the rollers, the intervalbetween the rollers is adjusted resulting in the wafer being clampedbetween the rollers. Since at least three rollers are provided aroundthe wafer, when the wafer is clamped by the rollers, the wafer is heldin a state in which the position in the radial direction is fixed.

At this time, as a result of the load control mechanism being operated,since the load applied from the rollers to the wafer in the radialdirection of the wafer is controlled, the interval between the rollersis adjusted so that the contact pressure between the rollers and waferis constant even if there are variations in the outer diameter dimensionof the wafer, thereby enabling variations in the outer diameterdimension of the wafer to be absorbed. When the rotation drive mechanismis operated while in this state, as a result of at least one of therollers being driven and rotated, the wafer is rotated about its axialcenter due to friction between the roller peripheral surface and thecircumferential surface of the wafer.

A load cell is provided in the interval adjustment mechanism thatdetects the load applied to the rollers along the direction of movementof the rollers, and the load control device may control the intervaladjustment mechanism so that the load detected by the load cell ismaintained constant.

In this case, as a result of the load applied to the rollers along thedirection of movement of the rollers being detected by the load cell andoperation of the load control apparatus, the interval adjustmentmechanism is controlled so that the load is constant. Thus, the contactpressure between the wafer and rollers is maintained constant at alltimes even during rotation of the wafer, and stable rotation of thewafer can be achieved by transmitting a constant torque from the rollersto the wafer.

In addition to the rollers being rotatably provided around axes arrangedroughly in the vertical direction, a flange section having a diameterlarger than the circumferential surface is provided below thecircumferential surface that clamps the wafer, and is composed of aninclined surface in which the upper surface of the flange sectiongradually becomes lower moving towards the outside in the radialdirection.

In this case, as a result of allowing the rollers to approach to asuitable dimension in which the radial dimension of an inscribed circleof the roller peripheral surface is slightly larger than the diameterdimension of the wafer, the radius dimension of an inscribed circle ofthe roller flange section can be made to be smaller than the diameterdimension of the wafer. When a wafer is inserted between the rollersfrom above the rollers while in this state, the wafer is placed on theflange section of the roller in the state in which an interval is formedbetween the circumferential surface of the wafer and the peripheralsurface of the roller.

Since the flange section is composed of an inclined surface that becomeslower moving towards the outside in the radial direction of the roller,the wafer is supported by the flange section only by the lower edge ofits circumferential surface. When rollers are allowed to approach fromthis state, it contacts the peripheral edges of the rollers so that thewafer rides up onto the upper surfaces of the flange sections composedof inclined surfaces. Thus, a wafer can be easily delivered from aprevious step to between the rollers and rotated simply by adjusting theinterval between the rollers.

The interval between the other two rollers adjacent to the roller onboth sides may be smaller than 180°. In the case a large flaw or notchhas been formed on the circumferential surface of a wafer, when thatflaw and so forth is arranged at the location of contact with one of therollers, the contact pressure between the roller and wafer suddenlyfluctuates and the wafer attempts to move in the direction of theroller. However, in this constitution, force acts in the direction thatinhibits movement of the wafer as a result of rollers being arranged onboth sides, thereby preventing the occurrence of misalignment duringrotation.

A pair of rollers may also be arranged at three locations or more atintervals in the circumferential direction of a wafer. In this case, asa result of the circumferential surface of the wafer being pushed fromroughly the same direction towards the inside in the radial direction bythe pairs of rollers, even if large flaws or notches in the wafercoincide with one of the rollers, the wafer is held by the other rollerso prevent fluctuation in the center position of the wafer.

An edge flaw inspection device of the present invention is provided witha wafer rotating device according to any of the rotating devicespreviously described, a light source that radiates light onto thecircumferential surface of a wafer supported by the wafer rotatingdevice, and a light detector that detects that light that has beenradiated from the light source which is reflected on the circumferentialsurface of the wafer.

According to this edge flaw inspection device, a wafer is rotated whilebeing supported only by its circumferential surface by the operation ofthe wafer rotating device. Thus, by radiating light from the lightsource while rotating the wafer, and then detecting the light reflectedby the circumferential surface of the wafer with the light detector,edge flaws over the entire circumferential surface of the wafer can beinspected without contacting the wafer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a wafer rotating device as claimed in anembodiment of the present invention.

FIG. 2 is a plan view showing the wafer rotating device of FIG. 1.

FIG. 3 is a plan view showing an interval adjustment mechanism of thewafer rotating device of FIG. 1.

FIG. 4 is a front view showing the shape of a roller of the waferrotating device of FIG. 1.

FIG. 5 is a front view showing the state of a wafer moving over theroller of FIG. 4.

BEST MODE FOR CARRYING OUT THE INVENTION

The following provides an explanation of preferred embodiments of thepresent invention with reference to the drawings. However, the presentinvention is not limited to each of the following embodiments, and forexample, the constituent features of these embodiments may be suitablycombined or the constitution of each embodiment may be substituted withother known constitutions.

As is shown in FIGS. 1 through 3, a wafer rotating device 1 of thisembodiment is provided with eight rollers 2, a rotation drive mechanism3 that rotates and drives these rollers 2, an interval adjustmentmechanism 4 that adjusts the interval dimensions between these rollers2, and a load control device 6 that controls the load applied fromrollers 2 to a silicon wafer 5 clamped between rollers 2.

The eight rollers 2 are supported two each on four brackets 7. Eachroller 2 is provided with a cylindrical surface 8 that contacts thecircumferential surface of silicon wafer 5 a shown in FIG. 4, and aflange section 9 that is adjacent to the cylindrical surface 8 in one ofthe axial directions. Flange section 9 is formed over its entirecircumference to of a larger diameter than the cylindrical surface 8.Flange section 9 is formed on an inclined surface 10 that graduallywidens to the outside in the radial direction as the edge surfaceadjacent to the cylindrical surface 8 moves away from cylindricalsurface 8 along the axial direction. A retaining section 11, which isformed to a diameter slightly larger than cylindrical surface 8 andwhich prevents silicon wafer 5 from coming off in the upward direction,is formed adjacent to cylindrical surface 8 in the other axialdirection.

As shown in FIG. 1, rollers 2 are rotatably attached to the brackets 7with the axis of rotation of each roller 2 in parallel. A pulley 12 isfastened to the end of each roller 2.

Brackets 7 are fastened to sliders to be described later so that theflange sections 9 of rollers 2 are arranged below the cylindricalsurfaces 8 of rollers 2.

As shown in FIGS. 1 and 2, for example, the rotation drive mechanism 3has a motor 13 and various pulleys and belts for transmitting therotational torque of the motor 13. More specifically, the rotation drivemechanism 3 is provided with the motor 13, a drive pulley 14 fastened tothe output shaft of motor 13, main pulleys 15 attached to each bracket 7able to rotate about axes parallel to the axes of rotation of rollers 2,main drive pulleys 15 a fastened to rotating shafts 17 of each mainpulley 15 and a first belt 16 running between two rollers 2 and pulleys12 provided on brackets 7, connecting pulleys 18 fastened to therotating shafts 17 of each main pulley 15, and second belt 19 throughfourth belt 21 running between the connecting pulleys 18 of the fourbrackets 7.

In the drawings, reference numeral 22 indicates a tensioner that adjuststhe tension of the third belt 20 to remain constant by being displacedduring movement of sliders 23 to be described later.

The interval adjustment mechanism 4 is provided with two pairs ofsliders 23 to which are fastened two brackets 7 each, linear guides 24that guide these sliders 23 in directions that cause them to approachand move away, and a direct-acting mechanism 25 that moves these sliders23 along linear guides 24. In the drawings, reference numeral 24 aindicates nuts that move over linear guides 24.

Brackets 7 are fastened to sliders 23 at a predetermined angle ofinclination so that all eight rollers 2 simultaneously make contact withan inscribed circle that coincides with the external diameter dimensionof the silicon wafer 5 being handled when the interval of two sliders 23is adjusted to a predetermined position.

As shown in FIG. 3, for example, direct-acting mechanism 25 is providedwith a motor 26, a ball screw 27 that is rotated and driven by motor 26,and nuts 28 that engage with the ball screw 27 and are attached to thesliders 23. Reverse threads are formed in both sides of ball screw 27roughly about the center, and two each of nuts 28 for sliders 23 areengaged with each threaded section 27 a and 27 b.

When motor 26 is rotated in one direction, ball screw 27 is rotated inone direction corresponding to that rotation, and nuts 28 engaged withball screw 27 are moved so as to approach or move away corresponding tothat rotation. As a result, the interval between sliders 23 attached tonuts 28 is adjusted, and the interval dimension between rollers 2fastened to sliders 23 is adjusted.

A load control device 6 has a load cell 29 arranged between one of thenuts 28 and sliders 23, and a control device (not shown) that controlsthe output of motor 26 of internal adjustment mechanism 4 correspondingto an output signal from the load cell 29. When silicon wafer 5 isclamped between rollers 2 and a load is applied to rollers 2, load cell29 arranged between nuts 28 and sliders 23 detects the load applied torollers 2 through brackets 7 and sliders 23. Thus, the interval betweenrollers 2 can be controlled so that the load applied to rollers 2remains constant by controlling the output of motor 26 of intervaladjustment mechanism 4 corresponding to the detected load.

The following provides an explanation of the operation of wafer rotatingdevice 1 as claimed in the present embodiment composed in this manner.

When silicon wafer 5 is clamped between rollers 2, interval adjustmentmechanism 4 is activated and the interval between rollers 2 is increasedby increasing the interval between sliders 23. In the state in which theinterval between cylindrical surfaces 8 of rollers 2 is larger than theouter diameter dimension of the silicon wafer 5 to be clamped, siliconwafer 5 that has been transported by a handling robot (not shown), forexample, is inserted between rollers 2 from above rollers 2.

Since flange sections 9 of a larger diameter than cylindrical surfaces 8of rollers 2 are provided on the lower portions of rollers 2, siliconwafer 5 that has been inserted from above rollers 2 is delivered fromthe handling robot to wafer rotating device 1 so as to be placed onflange sections 9 as shown with the broken lines in FIG. 5. Since theupper surface of flange sections 9 is composed of an inclined surface10, silicon wafer 5 is placed on rollers 2 by contacting the lower edgeof its circumferential surface with inclined surfaces 10 of flangesections 9.

Next, when interval adjustment mechanism 4 is operated, sliders 23 aremoved in the direction in which they approach each other, and theinterval between rollers 2 decreases. Whereupon, silicon wafer 5 risesas indicated by the arrow in FIG. 5 by following inclined surfaces 10formed in the upper surface of flange sections 9 of rollers 2, and isguided to the position where it is clamped by cylindrical surfaces 8 ofrollers 2.

When sliders 23 further approach each other, the circumferential surfaceof silicon 5 contacts the cylindrical surfaces 8 of all rollers 2. Whena contact load is generated between silicon wafer 5 and rollers 2, thatload is detected by load cell 29, and the detected load is controlled bythe control device so that it becomes a predetermined load.

While in this state, the rotational torque of motor 13 is transmitted toeach roller 2 through pulleys 12, 14, 15, 15 a and 18 and belts 16 and19 through 21 as a result of operating motor 13 of rotation drivemechanism 3. Silicon wafer 5 is rotated and driven due to frictionalforce proportional to the contact load between rollers 2 and siliconwafer 5.

At this time, silicon wafer 5 is stably held in position by balancinggravity and frictional force at a position in the direction of height ofany of cylindrical surfaces 8.

In this manner, according to wafer rotating device 1 as claimed in thepresent embodiment, silicon wafer 5 can be rotated without contactingthe top and bottom surfaces of silicon wafer 5.

In addition, since the load generated between rollers 2 and siliconwafer 5 when the circumferential surface of silicon wafer 5 is pressedby rollers 2 is controlled instead of controlling the positions ofrollers 2, even in the case in which there are variations in the outerdiameter dimension of silicon wafer 5, silicon wafer 5 can be suitablyclamped and rotated.

Moreover, since silicon wafer 5 is rotated by transmitting rotationaltorque from rollers 2 to the circumferential surface of silicon wafer 5,the task of indexing the center of rotation of silicon wafer 5 isunnecessary. Although transfer work was conventionally carried outconsisting of indexing the amount of eccentricity and changing thesuctioned location according to the rotating table by temporarilysuctioning a silicon wafer to the rotating table and then rotating therotating table, since this center of rotation indexing work and transferwork are no longer necessary, the number of steps can be significantlyreduced.

Moreover, since pairs of rollers 2 are arranged at four locations atintervals in the circumferential direction of silicon wafer 5, even if alarge flaw or V-shaped notch has been formed in the circumferentialsurface of silicon wafer 5, when that flaw and so forth makes contactwith one of the rollers 2, a shift in the center of rotation of siliconwafer 5 can be prevented. Namely, in the case a flaw formed in thecircumferential surface of silicon wafer 5 is located at a position thatmakes contact with a roller 2 due to rotation of silicon wafer 5,although silicon wafer 5 attempts to move towards the direction of thatroller 2 since the contact load between that roller 2 and silicon wafer5 fluctuates, silicon wafer 5 is held so as not to move by the otherrollers 2 that support silicon wafer 5 at nearly the same location.

According to the wafer rotating device 1 in the present embodiment,since all eight rollers 2 that simultaneously contact thecircumferential surface of silicon wafer 5 are rotated and driven by theoperation of rotation drive mechanism 3, since it is difficult forslippage to occur between silicon wafer 5 and rollers 2, together withbeing able to improve the angular accuracy, silicon wafer 5 can berotated at a comparatively high speed.

The edge flaw inspection device using the wafer rotating device 1 isprovided with a light source that radiates parallel light from theoutside in the radial direction of silicon wafer 5, and a light detectorthat detects reflected light on the circumferential surface of siliconwafer 5, outside wafer rotating device 1.

According to this edge flaw inspection device, since there is no contactmade with the top and bottom surfaces of silicon wafer 5, edge flaws canbe inspected even after polishing the top and bottom surfaces of siliconwafer 5.

In addition, since indexing of the center position of silicon wafers andtransfer work are not necessary, and silicon wafers can be rotated athigh speed, the inspection steps can be reduced thereby making itpossible to improve yield.

Moreover, since slippage between the rollers and silicon wafer isreduced when rotating the silicon wafer at high speeds thereby making itpossible to rotate the silicon wafer at a high degree of angularaccuracy, the locations of edge flaws can be detected with highprecision.

Although a constitution is employed in the present embodiment in whichthe rotational torque of motor 13 is transmitted to rollers 2 throughpulleys 12, 14, 15, 15 a and 18 as well as belts 16 and 19 through 21,other transmission mechanisms such as the use of gears may be employedinstead. Although ball screw 27 is employed for the direct-actingmechanism, another arbitrary mechanism such as a cylinder may beemployed instead.

Although pairs of rollers 2 are arranged at four locations, the numberof brackets 7 fastened to one slider 23 may be made to be one, and pairsof rollers 2 may be arranged at three locations in the circumferentialdirection of silicon wafer 5. Moreover, if a large number of rollers 2are used, instead of using in pairs, one roller each may be arranged atintervals.

INDUSTRIAL APPLICABILITY

According to the wafer rotating device of the present invention, a wafercan be rotated without suctioning the top and bottom surfaces of thewafer and without contacting the circumferential surface of the wafer.In addition, by controlling the contact load between the wafer and therollers that make contact with its circumferential surface, since thewafer is clamped between the rollers, the wafer can be suitably clampedand allowed to rotate even if there are variations present in thediameter dimension of the wafer.

According to the edge flaw inspection device provided with this waferrotating device, flaws formed in the circumferential surface can beinspected even after polishing the top and bottom surfaces of the wafer.Thus, flaws that expand or occur during wafer polishing can be detectedby inspecting after that polishing.

1. A wafer rotating device comprising: at least three rollers rotatablyprovided about axes arranged at parallel intervals and which rotate overa circumferential surface of a disk-shaped wafer; a rotation drivemechanism that rotates and drives at least one of the rollers; aninterval adjustment mechanism capable of adjusting dimensions of theintervals of the rollers; and a load control device that controls a loadapplied from the rollers to the wafer in a radial direction of the waferwhen the wafer is clamped between the rollers.
 2. The wafer rotatingdevice according to claim 1 wherein a load cell is provided in theinterval adjustment mechanism that detects the load applied to therollers along a direction of movement of the rollers, wherein the loadcontrol device controls the interval adjustment mechanism so that theload detected by the load cell is maintained constant.
 3. The waferrotating device according to claim 1 wherein the rollers are rotatablyprovided around the axes which are arranged roughly in a verticaldirection, and the rollers include a flange section and acircumferential surface wherein the flange section has a diameter largerthan the circumferential surface of the rollers, and the flange sectionis provided below the circumferential surface which clamps the wafer,and the flange section has an inclined surface in which an upper surfaceof the flange section gradually becomes lower moving towards an outsidein a radial direction.
 4. The wafer rotating device according to claim 1wherein, an angle between two of the rollers adjacent to one of therollers and on both sides of the one of the roller is smaller than 180°.5. The wafer rotating device according to claim 4 wherein pairs ofrollers are arranged at three or more locations at intervals in acircumferential direction of the wafer.
 6. An edge flaw inspectiondevice comprising: a wafer rotating device including: at least threerollers rotatably provided about axes arranged at parallel intervals andwhich rotate over a circumferential surface of disk-shaped wafer, arotation drive mechanism that rotates and drives at least one of therollers; an interval adjustment mechanism capable of adjustingdimensions of the intervals of the rollers, and a load control devicecontrols that controls a load applied from the rollers to the wafer in aradial direction of the wafer when the wafer is clamped between therollers, a light source that radiates light onto the circumferentialsurface of a wafer supported by the wafer rotating device; and a lightdetector that detects light that has been radiated from the light sourcewhich is reflected on the circumferential surface of the wafer.